A gigantic platypus may have swum in the waters of Australia about 5 million to 15 million years ago.

Scientists found a large fossil molar in the Riversleigh World Heritage Area and determined the tooth belonged to Obdurodon tharalkooschild, a new, extinct species of platypus. Paleontologists now know of four extinct and one living species of platypus.

Based on the size and shape of the tooth, the newly identified platypus species was about a meter long — twice the size of the living species of the mammal — and probably crunched through tortoises and other shelled prey, the researchers will report November 12 in the Journal of Vertebrate Paleontology.